1. Field of the Invention
This invention relates to circuits for receiving data from a data source such as a computer and presenting it to a display means.
2. Prior Art
Information generated by a computer is typically displayed on a cathode ray tube (CRT). Signals from the computer are used to deflect an electron beam which writes the information on a CRT screen. CRT screens are raster scanned to make the image. Raster scanning techniques involve forming a series of parallel horizontal beams drawn left to right, from the top of the screen to the bottom.
As miniaturization has increased, computers have become portable, and can now be made to operate on batteries. However, two disadvantages of CRT displays have limited the portability of computers. First, the size required by CRT displays makes them too bulky for some applications, such as lap use. Second, the power requirements of CRTs are such that they cannot be operated by batteries small enough to allow true portability.
One solution to these problems is the use if Liquid Crystal Displays (LDCs). LCDs can be made flat and light weight and have lower power requirements than CRTs, making them ideal portable displays.
The problem with utilizing LCDs as computer displays is the fact that the video output of a computer intended for a CRT display is not compatible with LCD displays. The response time for LCDs is slower than CRTs and the refresh rate (the rate at which displayed data must be updated) is different than that of CRTs.
The present invention proposes a solution to the above problem by the use of a circuit which allows a LCD to utilize output from a computer meant for a CRT display.